1. Field of the Invention
The present invention relates to an optical igniter comprising a pyrotechnic substance which is ignited by laser radiation fed to the pyrotechnic substance through an optical fiber.
2. Description of the Prior Art
In this type of optical igniter one end of the optical fiber is connected to a source of laser radiation and the other end of the fiber is inserted into a connector.
This type of optical igniter also includes means for providing a removable mechanical connection between the connector and the pyrotechnic substance.
An optical igniter of the above kind is described in an article published in 1997 in the journal xe2x80x9cEG and G Optoelectronicsxe2x80x9d and entitled xe2x80x9cCommercialization of a laser ignited actuatorxe2x80x9d.
In practice, the manufacture of an optical igniter of the above kind encounters many problems with obtaining perfect transmission of the laser radiation without loss of energy between the optical fiber and the pyrotechnic substance.
The object of the present invention is to overcome the above problems by providing a low-cost energy-efficient optical igniter which is simple to manufacture and assemble and totally reliable in operation.
The invention therefore provides an optical igniter including a pyrotechnic substance, an optical fiber one end of which is connected to a source of laser radiation and the other end of which is inserted in a connector, means providing a removable mechanical connection between the optical fiber connector and the pyrotechnic substance, and a glass rod between the optical fiber connector and the pyrotechnic substance whose axis is aligned with the axis of the optical fiber and which is made of graded index glass in one part or two coaxial parts in contact with the pyrotechnic substance and with the end of the optical fiber so that laser radiation from the end of the optical fiber passes through the glass rod and is focused onto the face of the glass rod in contact with the pyrotechnic substance.
Because the manufacture of an igniter of the above kind does not raise the problem of very accurate alignment of the optical fiber and the graded index glass rod, it can be done at low cost using standard technical resources.
Also, inserting the aforementioned glass rod between the optical fiber and the pyrotechnic substance achieves perfect transmission of the laser energy to the pyrotechnic substance, which makes the operation of the igniter totally reliable.
The graded index glass rod is preferably inserted in a bore formed in a member made of a material that is a poor conductor of heat. The material that is a poor conductor of heat can be a metal that is a poor conductor of heat, which excludes copper and aluminum. The above member can instead be made of a ceramic material.
In one version of the invention the member made from a material that is a poor conductor of heat is cylindrical or frustoconical.
Other features and advantages of the invention will become more apparent in the course of the following description, which is given with reference to the accompanying drawings, which are provided by way of non-limiting example only.